It is known to use wood-based multilayer composites for example in the form of lightweight building boards. Several examples of such composites are described in the following references.
Swiss Patent No. CH 254025 discloses a multilayer composite which comprises two cover boards and a core layer therebetween, the core layer comprising at least one layer of folded veneer.
German Patent No. DE 42 01 201 discloses a wooden semi-finished product or finished product which is made of laminar surface elements. The laminar elements can be zigzag-shaped. They can be randomly distributed together with surface elements or overlap in the manner of scales.
German Patent Application No. DE 10 2008 022 806 discloses a lightweight building board comprising a corrugated wood veneer layer. The waves can be zigzag-shaped.
Belgium Patent Application No. BE 547 811 discloses a core layer consisting of two zigzag-shaped wooden elements which are arranged between two cover layers.
German Patent Application No. DE 10 2008 022805 A1 discloses a corrugated veneer board and lightweight building boards constructed therefrom. The wave structure of the wooden elements used can be zigzag-shaped, sinusoidal and trapezoidal. The wooden elements can be stacked inside one another.
European Patent No. EP 1 923 209 discloses a lightweight building composite board comprising outer layers and a central layer, the central layer being arranged at an angle with respect to the plane of the lightweight building composite board.
A common feature of these multilayer composites from the prior art is that the core layer can have a loosened structure. When force is applied perpendicularly with respect to the surface of the multilayer composite, said multilayer composite has a damping effect since the core layer can be at least partially compressed.
These multilayer composites often require the use of high-quality starting products, since imperfections in the starting material cannot be tolerated or can only be tolerated to a small extent. In addition to the high quality of the raw materials, very high-quality corrugated webs are also required, since, inter alia, the cohesion between the individual layers can only be guaranteed at a relatively low pressure during production of the core layer. However, the low pressure during compression leads to the core layer obtained having a low dimensional stability. Although the formation of cavities has a favorable effect on the ratio of weight to stability, it can also lead to the core layer having impaired machinability in terms of drill machining and also the introduction and retaining capacity of standardized fittings, if for example nails or screws encounter cavities.
Improved retaining capacity of fittings of a core layer is disclosed in European Patent No. EP 2 660 408. This document discloses a core layer which is suitable for a multilayer composite that has at least one cover layer and a core layer, the cover layer being arranged so as to at least partially cover the core layer and be fixedly connected thereto, the core layer comprising zigzag-shaped elements made of wood which have laminar regions that are arranged in the shape of a zigzag, a zig region of an element together with an adjacent zag region of the zigzag-shaped element forming a common edge therebetween, and zigzag-shaped elements being arranged in the core layer such that two edges of this kind of two zigzag-shaped elements which can be the same or different from one another intersect at an angle that is different to zero, the two elements being fixedly interconnected at the intersection point.
International PCT Patent Publication No. WO 2015/067362 discloses a core layer which comprises zigzag-shaped wooden elements, preferably wooden elements having a wave structure, and is suitable for producing a multilayer composite or for production in a multilayer composite, preferably for producing a lightweight building board, and a multilayer composite which comprises the core layer.
A core layer comprising corrugated wooden elements is also disclosed in International PCT Patent Publication No. WO 2015/149942.
By randomly scattering wave-like particles, the three documents mentioned last provide core layers which, by comparison with the above-mentioned prior art, facilitate the production of a light, stable core layer or lightweight building board from significantly lower quality raw materials. Good processing of the lightweight building board, even in relation to the introduction of standardized fittings, is achieved by these core layers.
International Patent Publication No. WO 99/63180 discloses a laminar wooden component made of at least two layers glued together. At least one of the layers consists of a corrugated wooden layer that supports a further layer glued onto the rear of the wave at least on one side.
European Patent No. EP 2 873 522 discloses a composite board comprising a central layer having a cover layer made of a wooden material arranged in each case above and below said central layer, the central layer comprising corrugated slats.
The problem addressed by the present invention is that of providing a core layer and a multilayer composite in the form of a lightweight building board containing the core layer, which multilayer composite has improved stability with respect to conventional multilayer composites having the same density or which, if the multilayer composite has a decreased density, has comparable stability with respect to conventional lightweight building boards. It would be desirable to provide such a core layer and a multilayer composite to improve this art field.